JP2014059442A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective optical sensor configured to accurately detect a change in surface condition of a transfer member by accurately detecting reflected light of a fixing member, while maintaining excellent image quality, and to provide an image forming device.SOLUTION: A printer 100 for forming an image on a recording sheet S using toner includes: a reflective optical sensor 200 comprising an LED 211, an irradiation lens 221, a light-receiving lens 222, a PD 212, a substrate 210, a case 240, and a flat part 223 arranged on a boundary between the irradiation lens 221 and the light-receiving lens 222; and surface condition determination means 300 which detects a surface condition of a fixing belt 61 on the basis of a detection value from the reflective optical sensor 200.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine, or a plotter apparatus.

  2. Description of the Related Art Conventionally, image forming apparatuses that form color images using a plurality of color toners have been widely implemented as analog or digital color copiers, printers, facsimile machines, and the like. Recently, it has been widely implemented as a multifunction printer (MFP) or the like (for example, see Patent Documents 1 to 3). In such an image forming apparatus, an electrostatic latent image is written on the surface of the image carrier, and a developer such as toner is attached to the electrostatic latent image to form an image. Next, the image-formed image is transferred to a recording material such as paper, and the image transferred to the recording material is fixed by fixing means such as a fixing belt, thereby forming an image.

  Then, by repeatedly fixing the image, the surface of the fixing unit may be worn or scratched. Specifically, for example, in an image forming apparatus capable of using A4 size paper and A3 size paper as recording materials, fixing is repeated in a state in which A4 size paper is vertically fed (referred to as sending the paper vertically long). Then, on the surface of the fixing belt as the fixing unit, vertical streak-like scratches are generated at the positions where both end portions of the A4 longitudinal paper in the sheet width direction are located. This is caused by the surface of the fixing belt being worn by paper dust adhering to both ends of the paper (debris such as additives generated by cutting the paper). When such vertical streak-like scratches are formed on the fixing belt, fixing is performed using A4 landscape paper (referred to as sending the paper in landscape orientation) or A3 portrait paper. A glossy streak appears on the image surface corresponding to the vertical streak. The appearance of the gloss streaks causes image quality degradation.

  In the inventions described in Patent Literature 1 to Patent Literature 3, measures for preventing such deterioration in image quality are disclosed. For example, the image forming apparatus described in Patent Document 1 includes an optical sensor that irradiates the surface of the fixing roller with light from a light source and receives reflected light from the fixing roller. Based on the intensity of the reflected light captured by the optical sensor, the reflectance of the surface of the fixing roller is calculated. When the reflectance is equal to or less than a predetermined value, the image forming apparatus issues a warning alarm because the surface of the fixing roller is scratched, offset, or the surface is deteriorated. By issuing this warning alarm, it is possible to determine when to replace the fixing roller.

  However, in an endless belt-like fixing belt generally used as a fixing member, the distance to the light irradiation position and the angle of the irradiation position are likely to vary due to wobbling, fluttering, curling, etc. during rotation. Due to the influence, the reflected light from the fixing belt is irregularly reflected, so that an accurate value cannot be read by the optical sensor, and the optical performance is deteriorated. For this reason, a warning alarm may be issued even when it is not time to replace the fixing member.

  On the other hand, in the image forming apparatus described in Patent Document 2, the entire surface of the fixing member is worn to prevent the flaws from concentrating on a part of the image so that the flaws are not noticeable. However, there is no disclosure about detection of the occurrence of scratches or the state of scratches. Further, in the image forming apparatus described in Patent Document 3, when a scratch is detected, the portion corresponding to the scratch is developed with a larger amount of developer attached than the surrounding area, so that the scratch becomes inconspicuous. I am doing so. As a result, frequent replacement of parts, installation of new parts, and the like are not required, and costs can be reduced. In recent years, there has been further development of an image forming apparatus that can detect the occurrence of scratches on the fixing member and the state of the flaws in a more precise manner, respond quickly, and maintain high image quality. It has been demanded.

  The present invention has been made in view of the above circumstances, and a reflective optical sensor and an image capable of detecting a change in the surface state of a fixing member with higher accuracy and maintaining high image quality. An object is to provide a forming apparatus.

  In order to achieve the above object, a reflective optical sensor according to the present application is a reflective optical sensor that is used in an image forming apparatus that forms an image on a recording medium and detects a surface state of a moving body, and includes at least two A plurality of irradiation systems each having a light emitting unit; a plurality of irradiation lenses corresponding to the plurality of irradiation systems; an irradiation optical system for guiding light emitted from the irradiation system to a moving body; and at least two light receiving units A light receiving system and a light receiving optical system that has a light receiving lens corresponding to at least two light receiving units and guides the light reflected by the moving body to the light receiving system, and a plurality of irradiation lenses and light receiving lenses And a flat portion parallel to the optical axis direction at the boundary between the irradiation lens and the light receiving lens. It is characterized by having

  According to the present invention, a reflection-type optical sensor that can perform irradiation of light to a moving body and reception of reflected light with high accuracy without being affected by ghost light or the like, and has excellent optical performance. Can be provided. In addition, by using this reflective optical sensor, it is possible to obtain an image forming apparatus that can detect a change in the surface state of a moving body with higher accuracy and maintain high image quality. it can. Further, it is possible to reduce the maintenance cost of the image forming apparatus and the like by reducing the number of times of exchanging moving bodies such as fixing members as consumables.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. FIG. 2 is an enlarged side view showing a fixing unit in FIG. 1. It is a whole block diagram of a reflection type optical sensor and a surface state determination means. FIG. 7 is an explanatory diagram for explaining a state in which vertical streak-like scratches are generated on the surface of the fixing belt due to an edge portion of A4 vertical paper. It is explanatory drawing for demonstrating the structure of the reflective optical sensor which concerns on 1st Example, Comprising: (a) shows the schematic sectional drawing which observed the reflective optical sensor in the main scanning direction, (b) The schematic sectional drawing observed in the scanning direction is shown. FIG. 6 is a schematic cross-sectional view of the PD and the light receiving lens of the reflective optical sensor according to the first embodiment shown in FIG. It is explanatory drawing for demonstrating in detail the structure of the lens array of the reflection type optical sensor of 1st Example. It is a top view of the board | substrate which supports LED and PD of 1st Example. It is explanatory drawing for demonstrating reflection of the light by a flat part. It is explanatory drawing for demonstrating the structure of the reflection type optical sensor of a comparative example, Comprising: (a) shows the schematic sectional drawing which observed the reflection type optical sensor in the main scanning direction, (b) observed in the sub scanning direction. FIG. It is the schematic sectional drawing which observed PD and the lens for light reception of the reflective optical sensor of the comparative example in the subscanning direction. It is explanatory drawing for demonstrating the structure of the lens array of the reflection type optical sensor of a comparative example. It is a top view of the board | substrate which supports LED and PD of a comparative example. It is a flowchart which shows operation | movement of a reflection type optical sensor. It is a flowchart which shows operation | movement of a surface state determination means. In a comparative example, it is a schematic diagram using the reflected light intensity acquired in detection field A, (a) is a graph which shows the reflected light intensity acquired in detection field A, and (b) is reflected. It is a graph which shows the differential value of intensity | strength, (c) is a graph which shows the fall amount of reflected light intensity to the graph of (a). It is explanatory drawing for demonstrating the procedure which determines the position of a damage | wound, Comprising: (a) is a graph which shows the reflected light intensity acquired in the detection area A in a comparative example, (b) is a reflection intensity | strength. It is a graph which shows a differential value. It is explanatory drawing for demonstrating the procedure which determines a damage | wound level, Comprising: (a) is the graph which calculated | required the position which several points have gathered in the range of ± 20 with a small differential value with respect to the position of the damage | wound in a comparative example. (B) is a graph showing the depth of the flaw. It is the graph which expanded the vertical axis | shaft of FIG.18 (b). It is the graph which showed the PD output fluctuation | variation result of the reflection type optical sensor of a comparative example and a 1st Example. It is explanatory drawing for demonstrating the structure of the reflective optical sensor of 2nd Example, Comprising: (a) shows the schematic sectional drawing which observed the reflective optical sensor in the main scanning direction, (b) is the subscanning direction. The observed schematic sectional view is shown. It is the schematic sectional drawing which observed PD and the lens for light reception of the reflective optical sensor of 2nd Example in the subscanning direction. It is explanatory drawing for demonstrating in detail the structure of the lens array of the reflection type optical sensor of 2nd Example. It is a top view of the board | substrate which supports LED and PD of 2nd Example. It is the graph which showed the PD output fluctuation | variation result of the reflection type optical sensor of 1st Example and 2nd Example. It is explanatory drawing for demonstrating the structure of the reflective optical sensor of 3rd Example, (a) shows the schematic sectional drawing which observed the reflective optical sensor in the main scanning direction, (b) is the subscanning direction. The observed schematic sectional view is shown. It is the schematic sectional drawing which observed PD and the lens for light reception of the reflective optical sensor of 3rd Example in the subscanning direction. It is a top view of the board | substrate which supports LED and PD of 3rd Example. It is explanatory drawing for demonstrating the structure of the reflective optical sensor of 4th Example, (a) shows the schematic sectional drawing which observed the reflective optical sensor in the main scanning direction, (b) is the subscanning direction. The observed schematic sectional view is shown. It is the schematic sectional drawing which observed PD and the lens for light reception of the reflective optical sensor of 4th Example in the subscanning direction. It is explanatory drawing for demonstrating in detail the structure of the lens array of the reflective optical sensor of 4th Example. It is a top view of the board | substrate which supports LED and PD of 4th Example. It is the graph which showed the PD output fluctuation result of the reflective optical sensor of 1st Example in the operation example 2, (a) shows PD output distribution at the time of lighting one LED, (b) is three. The PD output distribution when the LEDs are simultaneously turned on is shown. It is explanatory drawing for demonstrating the irradiation position of a light spot, (a) shows the irradiation position of the light spot when a reflective optical sensor is arrange | positioned in parallel with the main scanning direction, (b) is a reflection type. The irradiation position of the light spot when the optical sensor is arranged in a direction inclined by 45 ° with respect to the main scanning direction is shown. FIG. 4 is a diagram in which a reflective optical sensor is disposed in the vicinity of an edge portion of a small-sized sheet, (a) is a diagram disposed in the vicinity of an edge section of A4 sheet, and (b) is disposed in the vicinity of an edge section of A5 sheet. (C) is a diagram arranged in the vicinity of the edge portion of A6 paper. FIG. 6 is a schematic diagram showing a state in which a reflective optical sensor formed largely in the main scanning direction is arranged on a fixing belt.

  A reflective optical sensor according to the present application is a reflective optical sensor that is used in an image forming apparatus that forms an image on a recording medium and detects a surface state of a moving body, and includes a plurality of irradiation systems having a light emitting unit, and From irradiation means comprising an irradiation optical system having a plurality of irradiation lenses, a light receiving system having a light receiving portion for receiving reflected light reflected by the moving body, and a light receiving optical system having a light receiving lens corresponding to the light receiving portion Light receiving means.

  Further, since the irradiation lens and the light receiving lens are integrated, it is possible to improve the workability when assembling each lens to the reflective optical sensor and to increase the placement accuracy between the lens surfaces. In this integration, it is preferable that all the irradiation lens and the light receiving lens are integrally formed. However, a plurality of integrated ones of the irradiation lens and the light receiving lens are arranged. The structure etc. to perform may be sufficient.

Further, the plurality of irradiation lenses and the light receiving lens are arranged so that the lens centers are different from each other with respect to the optical axis direction. With such a configuration, while maintaining the amount of light received by each light receiving unit, the output variation of the light receiving unit due to the angle variation (particularly, the tilt angle variation) of the moving body (detection surface) with respect to the reflective optical sensor is suppressed. can do.

  Also, by providing a flat part (step) parallel to the optical axis direction at the boundary part between the irradiation lens and the light receiving lens, light is reflected by this flat part. Light other than detection light necessary for detection (hereinafter referred to as “ghost light”) can be reduced. Therefore, the reflective optical sensor according to the present application is excellent in optical performance and can be suitably used for an image forming apparatus or the like. Note that the “parallel flat portion” here is a flat surface that is strictly parallel to the optical axis direction, but is substantially substantially free of slight errors such as unevenness and inclination. It is also included that it is a parallel flat surface. As described below, it is only necessary to reflect light and reduce light other than detection light necessary for detecting the surface state of the moving body.

  Moreover, in the reflective optical sensor according to the present application, it is preferable that the light emitting units of the irradiation system are arranged symmetrically with respect to the optical axis of the corresponding illumination lens. With this configuration, the surface of the moving body can be irradiated with light at substantially equal intervals, and uniform detection on the moving body becomes possible. Note that the line object here includes not only a strict line object but also a substantially line object.

  Further, in the reflective optical sensor according to the present application, it is preferable that the light receiving lens is disposed at a position away from the light receiving system in the optical axis direction as compared with the irradiation lens. By arranging the light receiving lens at a position far away from the irradiation system side with respect to the optical axis direction of the lens as compared with each irradiation lens, the radius of curvature of the light receiving lens can be increased. Therefore, it is possible to satisfactorily suppress the deterioration of the optical performance at the lens end of the light receiving lens. As a result, particularly when the moving body is a fixing member that fixes an image, fluctuations in the light receiving unit output of the reflective optical sensor due to variations in the tilt angle of the fixing member can be reduced more favorably.

  In the reflective optical sensor according to the present application, the light receiving lens is preferably a cylindrical lens that focuses light only in one axis direction. Thus, by making the light-receiving lens a single cylindrical lens, there is no variation in lens parameters (for example, lens curvature radius, lens position, lens thickness, etc.) between individual lenses. Therefore, the surface state of the moving body can be detected with higher accuracy.

  In addition, by using a light-receiving lens as a cylindrical lens with no power in the main scanning direction, it is possible to suppress changes in the amount of received light at the light-receiving unit due to differences in the illumination system that is lit, compared to a spherical lens. Can do. Therefore, it becomes possible to detect the surface state of the moving body with higher accuracy.

  In the reflective optical sensor according to the present application, it is preferable to provide an opening between the irradiation system and the illumination optical system. By providing an opening in this manner, light that is transmitted to another moving lens through an irradiation lens other than the irradiation lens corresponding to the arbitrary irradiation system to be turned on, and further, arbitrary irradiation that is turned on Directly reflected light from the lens surface of other illumination lenses other than the illumination lens corresponding to the illumination system or the illumination lens corresponding to any illumination system that is lit (hereinafter referred to as “flare light”) However, it can prevent entering into a light-receiving part directly. Therefore, the surface state of the moving body can be detected with higher accuracy. Further, when the opening is provided, the step of the flat portion can be used as the reference plane, so that the positional accuracy of the opening can be improved and the optical performance of the reflective optical sensor can be improved.

  Moreover, it is preferable that the reflective optical sensor according to the present application sequentially irradiates the surface of the moving body with the light spot from the light emitting units of a plurality of irradiation systems. In this way, by sequentially irradiating a plurality of light spots, crosstalk (when viewed from one light receiving unit, reflected light from a plurality of irradiation systems is received simultaneously as compared with the case of irradiating simultaneously. ) Will disappear. For this reason, it is possible to improve the detection accuracy of the detection result obtained for the position irradiated with each light spot in the main scanning direction.

  Or the reflective optical sensor which concerns on this application may irradiate a light spot simultaneously on the surface of a moving body from the light emission part of several irradiation system. In this way, by irradiating a plurality of light spots at the same time, the line period (the time required to turn on all the irradiation systems) can be shortened as compared to the case of sequentially irradiating. Since it can be detected in a short time, it is possible to reliably detect a scratch on the surface of the moving body. For such sequential irradiation and simultaneous irradiation, it is preferable to select a suitable one according to the purpose of use of the reflective optical sensor, the degree of scratches, the usage environment, and the like.

  Moreover, in the reflective optical sensor according to the present application, it is preferable that a plurality of light spots are emitted from the light emitting units of the plurality of irradiation systems with an arbitrary inclination with respect to the detection direction of the surface of the moving body. In this case, a plurality of irradiation systems may be arranged to be inclined with respect to the detection direction of the moving body, that is, the main scanning direction. Alternatively, the plurality of illumination systems are arranged in parallel to the main scanning direction, but when the light spot is irradiated from the irradiation system, the light spot row may be irradiated so as to be inclined with respect to the main scanning direction. . In either case, the arrangement pitch of the light spot rows changes between when the light spot row is irradiated in parallel with the main scanning direction and when the light spot row is irradiated at an angle. When the light spot row is irradiated with being inclined with respect to the main scanning direction, the arrangement pitch of the light spots in the main scanning direction can be reduced. Therefore, the position resolution can be easily improved.

  Further, the reflective optical sensor according to the present application may be partially arranged with respect to the end position of the recording medium conveyed by the moving body or the vicinity thereof, or may be arranged over the entire width of the recording medium. . With such an arrangement, when a small-size sheet is used as a recording material, the detection area including the edge portion can be reduced, so that the reflective optical sensor can be reduced in size.

  In the reflective optical sensor according to the present application, it is preferable that the length of the plurality of irradiation systems in the arrangement direction is the same as the length of the moving body in the arrangement direction. With this configuration, the length of the reflective optical sensor in the main scanning direction is sufficiently large so as to be compatible with various paper sizes, and even if scratches appear at different locations on the moving body depending on the paper size, it is ensured. Can be detected. In addition, it is preferable that the lengths of the two are exactly the same, but it is only necessary that the lengths are substantially the same, and detection without leakage is possible.

  The image forming apparatus of the present application uses a reflection type optical sensor having excellent optical performance as described above as a reflection type optical sensor for detecting the surface state of a moving body that fixes an image on a recording medium. Therefore, it is possible to detect the scratch on the surface of the moving body with high accuracy, and to maintain high-accuracy image quality. In addition, it is possible to provide an image forming apparatus that can reduce the number of replacements of the moving body and reduce the maintenance cost.

  In the image forming apparatus according to the present application, the moving body is preferably an endless belt-like fixing belt. Since the surface of the fixing belt is made of a material having a high surface hardness such as PFA, the surface is particularly easily damaged. However, in the image forming apparatus of the present application, by using the reflection type optical sensor as described above, it is possible to detect the surface state of the fixing belt with high accuracy and quickly know the occurrence of a flaw. Therefore, it is possible to take measures such as preventing the recording material from passing through the area where the flaw is present, it is possible to lengthen the replacement period of the fixing belt, and to effectively use the fixing belt.

<First embodiment>
The image forming apparatus according to the first embodiment of the present application will be described below with reference to the drawings. In this embodiment, the image forming apparatus is applied to a tandem type full-color printer (hereinafter simply referred to as “printer”). The image forming apparatus referred to in the present application is not limited to a printer, but includes a copying machine, a facsimile machine, a printing machine, and an apparatus that combines these functions. The printer of this embodiment forms an image using toners of four colors of yellow, cyan, magenta, and black, and is provided with members corresponding to the respective colors. Hereinafter, in the description and drawings of the present specification, Y is added to the end of the reference numeral, M is added to the magenta member, C is added to the cyan member, and BK is added to the black member. Display or explain.

  As shown in FIG. 1, the printer 100 of this embodiment employs a tandem structure in which photosensitive drums 20Y, 20C, 20M, and 20BK as image carriers are arranged in parallel. These photosensitive drums 20Y, 20C, 20M, and 20BK can form images (images) corresponding to colors separated into yellow, cyan, magenta, and black, respectively.

  An outline of the configuration of the printer of this embodiment will be described. As shown in FIG. 1, the printer 100 according to the present embodiment performs charging and developing processes on the photosensitive drums 20Y, 20C, 20M, and 20BK as image carriers for each of yellow, cyan, magenta, and black. Four image stations 1Y, 1C, 1M, and 1BK, an optical scanning unit 8 as an exposure unit (optical writing unit), a transfer belt unit 10 and a secondary transfer roller 5 as transfer units, and an intermediate transfer belt cleaning unit 13 And a fixing unit 6 as a fixing means, a reflective optical sensor 200 (see FIG. 2) as a reflective optical detection means, and a surface state determination means 300 (see FIG. 2). .

  Further, the printer 100 includes a sheet feeding unit 80 as a paper feed cassette for the recording paper S as a recording medium, a pair of registration rollers 4 that convey the recording paper S, and a pair of registration rollers 4 with the leading ends of the recording paper S. It further has a sensor (not shown) for detecting that it has reached. The sheet feeding unit 80 is loaded with a recording sheet S that is transported between the photosensitive drums 20Y, 20C, 20M, and 20BK and an intermediate transfer belt 11 described later. The pair of registration rollers 4 transfers the recording sheet S conveyed from the sheet feeding unit 80 to each photosensitive drum 20Y at a predetermined timing according to the timing of toner image formation by the image stations 1Y, 1C, 1M, and 1BK. , 20C, 20M, 20BK and the intermediate transfer belt 11 toward the transfer portion.

  Further, the printer 100 includes a paper discharge roller 7 for discharging the recording paper S fixed by the fixing unit 6 to the outside of the main body of the printer 100, a paper discharge tray 17, and toner bottles 9Y, 9C, 9M, and 9BK. Is provided. The fixing unit 6 fixes the toner image on the recording paper S on which the toner image is transferred. The paper discharge tray 17 is provided in the upper part of the main body of the printer 100 and stacks the recording paper S discharged to the outside of the main body of the printer 100 by the paper discharge roller 7. The toner bottles 9Y, 9C, 9M, and 9BK are positioned below the paper discharge tray 17 and are filled with toners of yellow, cyan, magenta, and black.

  The transfer belt unit 10 is provided above the photosensitive drums 20Y, 20C, 20M, and 20BK, and includes an intermediate transfer belt 11 and primary transfer rollers 12Y, 12M, 12C, and 12BK. The secondary transfer roller 5 is a transfer roller provided to face the intermediate transfer belt 11, and is driven by the intermediate transfer belt 11. The intermediate transfer belt cleaning unit 13 is provided to face the intermediate transfer belt 11 and cleans the surface of the intermediate transfer belt 11. The optical scanning means 8 is disposed below the four image stations 1Y, 1C, 1M, and 1BK.

  The transfer belt unit 10 includes a driving roller 72 and a driven roller 73 around which the intermediate transfer belt 11 is wound, in addition to the intermediate transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12BK.

  The driven roller 73 also has a function as tension urging means for the intermediate transfer belt 11. Therefore, the driven roller 73 is provided with a biasing means 74 using a spring or the like. The primary transfer rollers 12Y, 12C, 12M, 12BK and the secondary transfer roller 5 of the transfer belt unit 10 and the intermediate transfer belt cleaning unit 13 constitute the second transfer unit 71.

  An intermediate transfer belt 11 (which also functions as a second image carrier) serving as a first transfer unit is disposed at a position facing each of the photoconductive drums 20Y, 20C, 20M, and 20BK, and the photoconductive drums 20Y, 20C. , 20M, and 20BK are transferred, and can be moved in the direction of arrow A1 in FIG. An endless belt is used as the intermediate transfer belt 11. The primary transfer process is performed on the intermediate transfer belt 11 to superimpose and transfer the respective images. Thereafter, the second transfer unit 71 performs the secondary transfer process on the recording paper S on which a recording sheet or the like is used. The batch transfer is performed by executing.

  The superimposed transfer with respect to the intermediate transfer belt 11 refers to a visible image formed on each of the photosensitive drums 20Y, 20C, 20M, and 20BK in the process of moving the intermediate transfer belt 11 in the A1 direction. It is said that it is transferred to the same position. The primary transfer rollers 12Y, 12C, 12M, and 12BK are disposed so as to face each of the photosensitive drums 20Y, 20C, 20M, and 20BK with the intermediate transfer belt 11 interposed therebetween so that such superposition transfer is possible. . The transfer by the primary transfer rollers 12Y, 12C, 12M, and 12BK is performed by shifting the timing from the upstream side to the downstream side in the A1 direction by applying a voltage.

  Although not shown in detail, the intermediate transfer belt cleaning unit 13 provided in the second transfer unit 71 is provided with a cleaning brush and a cleaning blade provided to face and contact the intermediate transfer belt 11. have. With these cleaning brush and cleaning blade, foreign matter such as residual toner on the intermediate transfer belt 11 is scraped off to remove the intermediate transfer belt 11. Further, the intermediate transfer belt cleaning unit 13 has a discharge unit (not shown) for carrying out and discarding the residual toner removed from the intermediate transfer belt 11.

  As described above, the printer 100 having the configuration shown in FIG. 1 has the color image superimposed by sequentially transferring the images formed on the photosensitive drums 20Y, 20C, 20M, and 20BK to the intermediate transfer belt 11. In this system, the secondary transfer roller 5 collectively transfers the material onto the recording paper S. However, the image forming apparatus of the present application is not limited to this. Instead of such a system, the recording paper S is carried on the intermediate transfer belt 11 and the recording paper S is loaded on each of the photosensitive drums 20Y, 20C, It is also possible to use a method in which images of the respective colors are directly superimposed on the recording paper S in opposition to 20M and 20BK.

  The photosensitive drums 20Y, 20C, 20M, and 20BK for forming yellow, cyan, magenta, and black images are arranged in this order from the upstream side in the A1 direction. Around the photosensitive drums 20Y, 20C, 20M, and 20BK, image stations 1Y, 1C, 1M, and 1BK for charging and developing processing are arranged according to these rotations. As the image stations 1Y, 1C, 1M, and 1BK, charging means 30Y, 30C, 30M, and 30BK, developing means 40Y, 40C, 40M, 40BKY, and 1BK are arranged along the rotation direction of the photosensitive drums 20Y, 20C, 20M, and 20BK. Next transfer rollers 12Y, 12C, 12M, 12BK and cleaning means 50Y, 50C, 50M, 50BK are arranged. The optical scanning unit 8 is used for writing performed after charging.

  The optical scanning unit 8 in this embodiment includes a semiconductor laser, a coupling lens, an fθ lens, a toroidal lens, a mirror, a rotating polygon mirror, and the like as a light source of the writing light Lb. The coupling lens is a lens that converts laser light into a substantially parallel light beam. This substantially parallel light beam (writing light Lb) is polarized by the polarization reflection surface of the rotary polygon mirror, and passes through an fθ lens, a toroidal lens, and a mirror. The upper surfaces of the photosensitive drums 20Y, 20C, 20M, and 20BK are irradiated as light spots. The light spot moves in the longitudinal direction with respect to the surfaces of the photosensitive drums 20Y, 20C, 20M, and 20BK as the rotary polygon mirror rotates, thereby scanning the surface. In this way, the optical scanning unit 8 emits the writing light Lb corresponding to each color to each of the photosensitive drums 20Y, 20C, 20M, and 20BK, and these photosensitive drums 20Y, 20C, 20M, and 20BK. An electrostatic latent image is formed on the surface.

  The sheet feeding unit 80 is provided at the lower part of the main body of the printer 100 and includes a feeding roller 3 that abuts on the upper surface of the uppermost recording sheet S. When the feeding roller 3 is driven to rotate counterclockwise, the uppermost recording sheet S is fed toward the pair of registration rollers 4.

  The fixing unit 6 uses a belt fixing system. As a configuration for this, a fixing belt 61, a heating roller 62 and a pressure roller 63, which are wound around the fixing belt 61 and have a heat source, and pressure are used. A fixing roller 64 around which the fixing belt 61 is wound is provided so as to face the roller 63. The configuration of the fixing unit 6 will be described in detail below.

  FIG. 2 is a diagram illustrating a configuration of the fixing unit 6. As shown in FIG. 2, the fixing unit 6 includes a pressure roller 63 as a pressure body, a fixing belt 61 as a moving body, a heating roller 62 around which the fixing belt 61 is wound, and a pressure roller 63. A fixing roller 64 around which the fixing belt 61 is wound, a tension roller 65 that applies tension to the fixing belt 61, a separation claw 67 provided downstream of the recording sheet S in the traveling direction of the nip portion, and heating. And a temperature sensor (not shown) for detecting the temperature of the fixing belt 61 on the roller 62. Hereinafter, the axial direction (the width direction of the fixing belt 61) of the heating roller 62 around which the fixing belt 61 is wound is referred to as a main scanning direction, and the rotation direction of the fixing belt 61 is referred to as a sub-scanning direction.

  The pressure roller 63 is provided with an elastic layer made of silicone rubber or the like on the surface of a core bar made of aluminum or iron, and a release layer made of PFA or PTFE is provided on the surface layer. The fixing belt 61 is configured by a base material such as nickel or polyimide having a release layer such as PFA or PTFE, or an elastic layer such as silicone rubber provided between them. The fixing belt 61 is wound around a fixing roller 64 and a heating roller 62, and is maintained at an appropriate tension by a tension roller 65 from the outside. The fixing roller 64 has a metal core and silicone rubber. The heating roller 62 is an aluminum or iron hollow roller, and has a heat source H such as a halogen heater inside.

  In the fixing unit 6 including such a member, a nip portion 66 is formed by the fixing roller 64 and the pressure roller 63 to convey the recording paper S while nipping it. The recording sheet S enters the nip 66 from below. When the recording paper S enters, the image on the recording paper S is fixed at the nip portion 66 by applying a predetermined pressure and heat.

  The tension roller 65 has a metal core and silicone rubber. The separation claw 67 has a sharp apex at the apex that is in contact with the surface of the fixing roller 64, and a plurality of the separation claws 67 are provided in the axial direction of the fixing roller 64 (direction perpendicular to the paper surface). In addition, as a temperature sensor for monitoring the temperature of the fixing unit 6, one non-contact temperature sensor (thermopile) that does not contact the fixing belt 61 is provided. Note that the present application is not limited to this, and a contact-type temperature sensor (thermistor) that contacts the fixing belt 61 can also be used.

  As shown in FIG. 4, for example, when the fixing unit 6 repeatedly fixes A4 size paper in the state of longitudinal paper, edges on both sides of the A4 longitudinal paper in the paper width direction on the surface of the fixing belt 61. Longitudinal streaks may occur at the position where the part passes. This occurs when the surface of the fixing belt 61 is worn by paper dust adhering to the end face of the edge portion. At this time, when the A4 landscape paper or the A3 portrait paper is fixed after the A4 portrait paper is fixed, a glossy streak appears on the image surface corresponding to the vertical streak. It will cause quality degradation.

  In order to solve this problem, in the present application, the surface state of the fixing belt 61 is determined using the reflective optical sensor 200 and the surface state determination unit 300. FIG. 3 shows an outline of the arrangement state of the reflection type optical sensor 200 and the surface state determination means 300. As shown in FIG. 3, the reflective optical sensor 200 is disposed to face the fixing belt 61 on the heating roller 62.

  The reflective optical sensor 200 is a sensor that irradiates a plurality of light spots in the main scanning direction toward the surface of the fixing belt 61 and receives reflected light from the fixing belt 61. The surface state determination unit 300 is connected to the reflective optical sensor 200 and is disposed in the printer 100, and receives the detection signal from the reflective optical sensor 200 to determine the surface state of the fixing belt 61.

  As the surface state determination unit 300, a main body control unit that drives and controls each unit of the printer 100 may be used in combination. The main body control means includes a CPU (Central Processing Unit) that executes various calculations and drive control of each part, a ROM (Read Only Memory) that stores fixed data such as computer programs in advance, and a work area that stores various data in a rewritable manner And a RAM (Random Access Memory) functioning as the same. In addition, this application is not limited to this, It is good also as the surface state determination means 300 using a control means etc. different from a main body control means.

  FIG. 4 shows a view of FIG. 3 viewed from a direction perpendicular to the axis of the heating roller 62 (main scanning direction). As shown in FIG. 4, the reflective optical sensor 200 has an end portion in the paper width direction of A4 longitudinal paper in the main scanning direction on the surface of the fixing belt 61 (hereinafter, the end portion is referred to as an “edge portion”). One is arranged on one side. The reflective optical sensor 200 forms a long detection region A on the surface of the fixing belt 61 by irradiating a plurality of light spots in the main scanning direction. Thus, since the reflective optical sensor 200 can form a long detection region A, the relative positional relationship between the reflective optical sensor 200 and the paper edge portion in the main scanning direction may not be strict.

  By receiving the detection signal from the reflective optical sensor 200, the surface state determination unit 300 can detect the surface state of the detection region A that is long in the main scanning direction. When the paper edge portion is included in the detection area A, the surface level of the fixing belt 61 is quantified as the surface state of the fixing belt 61 and / or the vertical streak-like scratch level formed by the paper edge portion. Details of the quantification will be described later. Here, the scratch level represents the degree of the scratch. That is, it refers to the depth (roughness) of the scratch and the width (size) of the scratch.

[Configuration of reflective optical sensor]
FIG. 5 shows an outline of the reflective optical sensor 200 (200a) according to the first embodiment. In FIG. 5, the x direction is the main scanning direction of the fixing belt 61, the y direction is the sub scanning direction, z is the direction perpendicular to the xy plane, and the reflective optical sensor 200 a faces the fixing belt 61. To do. The same applies to the following examples and comparative examples.

  FIG. 5A is a cross-sectional view of the reflective optical sensor 200a of the first embodiment observed in the main scanning direction (x direction). As shown in FIG. 5A, the reflective optical sensor 200a of the first embodiment is radiated with a light emitting diode (hereinafter referred to as “LED”) 211a as a light emitting unit (that is, an irradiation system). An irradiation optical system having an irradiation lens 221a arranged to irradiate the light spot SP with light guided to the surface of the fixing belt 61, and a reflection light reflected from the fixing belt 61 are arranged to be guided. A light-receiving optical system having a light-receiving lens 222a, a photodiode (hereinafter referred to as “PD”) 212a as a light-receiving unit that receives reflected light guided by the light-receiving lens 222a, and a substrate that supports the LEDs 211a and PD 212a 210a and a case 240a that holds the substrate 210a and the lens array 220a. Further, a flat portion (step) 223a formed of a flat surface parallel to the optical axis direction is formed at the boundary between the irradiation lens 221a and the light receiving lens 222a.

  The lens array 220a is formed by integrating a plurality of irradiation lenses 221a and one light receiving lens 222a in a two-dimensional array.

  FIG. 5B is a schematic cross-sectional view of the reflective optical sensor 200a of FIG. 5A observed in the sub-scanning direction (y direction). FIG. 6 is a schematic sectional view of the PD 212a and the light receiving lens 222a of the reflective optical sensor 200a of FIG. 5A observed in the sub-scanning direction (y direction). FIG. 7 is a diagram showing the irradiation lens 221a and the light receiving lens 222a in more detail with respect to the reflective optical sensor 200a. FIG. 8 is a plan view of a substrate that supports the LED 212a and the PD 212a. In the schematic cross-sectional views shown in FIGS. 5 (a), 5 (b), and 6, the front side of the case 240a is removed and the rear member is shown for convenience of explaining the inside of the reflective optical sensor 200a. Abbreviated. The same applies to the following examples and comparative examples.

  As shown in FIGS. 5B and 8, a plurality of LEDs 211a are arranged in the main scanning direction. In addition, one irradiation lens 221a is disposed corresponding to the four LEDs 211a. In this embodiment, the lens diameter of the irradiation lens 221a in the main scanning direction is 2.4 mm as an example. In this case, the arrangement pitch of the four LEDs 211a in the main scanning direction is P (see FIG. 8). Further, as indicated by dotted lines in FIG. 5B, the four LEDs 211a have light that is a line object with respect to the optical axis of the irradiation lens 221a. In the present embodiment, the light from the first LED and the light from the fourth LED in each unit are line targets with respect to the optical axis, and from the second LED and the third LED. Is a line object with respect to the optical axis. Therefore, as shown in FIG. 5B, the surface of the fixing belt 61 can be irradiated with the light spot SP row at substantially equal intervals (interval P ″).

  Here, when the surface state of the fixing belt is detected by the reflective optical sensor, the distance and angle variation of the detection surface with respect to the reflective optical sensor are affected by fluctuations of the fixing belt, fluctuation of the fixing belt, curling of the fixing belt, and the like. May occur. It is difficult to eliminate them completely. As described above, if there is a variation in the distance or angle between the reflective optical sensor and the detection surface, the correct output cannot be read when detecting the surface state of the fixing belt, and accurate detection cannot be performed. Therefore, there has been a problem that the influence of angular variation (hereinafter referred to as “tilting angle”) caused by the wave of the fixing belt among the distance and angular variation of the detection surface with respect to the reflective optical sensor is particularly large. .

  Therefore, in the reflective optical sensor 200a of the first embodiment, as the irradiation lens 221a, as shown in FIGS. 5A and 5B, an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction is used. ing. By using such an anamorphic lens, the spot diameter (beam diameter) of the light spot SP in the main scanning direction on the fixing belt 61 is maintained in a desired state, and the curvature radius in the sub-scanning direction of the lens is appropriate. Can be Therefore, it is possible to reduce the beam diameter in the sub-scanning direction of the reflected light incident on the light receiving lens 222a, and to reduce fluctuations in the light receiving unit output when the tilt angle varies due to the wave of the fixing belt 61. it can. As a result, it is possible to prevent the detection accuracy of the reflective optical sensor 200a from deteriorating and maintain excellent optical performance.

  The reflective optical sensor 200a of the first embodiment differs from the reflective optical sensor 200 'of a comparative example described later in the following three points. In particular, the following (2) is the main feature point of the first embodiment.

(1) No light shielding wall is provided.
(2) The irradiation lens 221a and the light receiving lens 222a are arranged at different positions in the optical axis direction.
(3) The lens parameters (curvature radius, lens diameter, lens thickness, distance between the center of the irradiation system and the irradiation lens, distance between the centers of the light receiving system and the light receiving lens, etc.) are different.

  The lens center positions of the irradiation lens 221 and the light receiving lens 222a of (1) are shifted from each other by about 0.25 mm in the optical axis direction. Therefore, compared with the light receiving lens 222a, the irradiation lens 221a is disposed at a position closer to the irradiation system (LED 211a) in the optical axis direction.

  Specifically, the lens parameter (3) has a radius of curvature of 4.6 mm in the main scanning direction (x direction in FIG. 5 and the like) of the irradiation lens 221a, and a conic constant in the main scanning direction is zero. The radius of curvature of the irradiation lens 221a in the sub scanning direction (y direction in FIG. 5 and the like) is 4.3 mm, and the conic constant in the sub scanning direction is −2.0. The irradiation lens 221a has a lens diameter in the main scanning direction of 2.4 mm, a lens diameter in the sub scanning direction of 9.2 mm, and a lens thickness of 6.6 mm.

  The radius of curvature of the light receiving lens 222a in the main scanning direction is 50 mm, and the conic constant in the main scanning direction is -1.0. The radius of curvature of the light receiving lens 222a in the sub-scanning direction is 4.8 mm, and the conic constant in the sub-scanning direction is −1.6. The light receiving lens 222a has a lens diameter in the main scanning direction of 17 mm, a lens diameter in the sub scanning direction of 10.9 mm, and a lens thickness of 6.35 mm.

  The distance between the centers of the irradiation lens 221a and the light receiving lens 222a in the sub-scanning direction (the distance between the optical axes) is 2.53 mm. The distance between the centers of the irradiation system (LED 211a) and the irradiation lens 221 in the optical axis direction is 10.37 mm, and the distance between the centers of the light receiving system (PD 212a) and the light reception lens 222a in the optical axis direction is 10.62 mm. is there. With such dimensions, as described above, the lens center positions of the irradiation lens 221a and the light receiving lens 222a are shifted from each other by about 0.25 mm in the optical axis direction.

  A set of four LEDs 211a and one irradiation lens 221a is hereinafter referred to as “one unit”. A plurality of these 1 units are arranged in the main scanning direction to constitute an irradiation means (irradiation system + irradiation optical system) of the reflective optical sensor 200a. In this case, as shown in FIG. 8, the arrangement pitch of one unit in the main scanning direction is P ′. Further, in order from the left side of FIG. 8, units 1, 2,. A plurality of units can be arranged corresponding to the length of the detection area A of the fixing belt 61. However, in order to simplify the following description, the units in this embodiment, the following embodiments, and the comparative example are used. The number is 7 (L = 7).

  In one unit, the light emitted from each LED 211 is irradiated on the surface of the fixing belt 61 as a light spot SP through the corresponding irradiation lens 221a. Therefore, as shown in FIG. 5B, a plurality of light spots SP are irradiated on the fixing belt 61 from the reflective optical sensor 200 in the main scanning direction at an arrangement pitch P ″.

  FIG. 6 is a back view of the PD 212a and the light receiving lens 222a of the reflective optical sensor 200a of FIG. 5A observed in the sub-scanning direction (y direction). As shown in FIGS. 6 and 8, a plurality of PDs 212a are arranged in the main scanning direction so as to face the LEDs 211a. At this time, the arrangement pitch in the main scanning direction is Pa '' '. Here, in the reflective optical sensor 200a of the first embodiment, as shown in FIGS. 5 and 8, Pa ′ ″ (the arrangement pitch of the PDs 212a) ≈Pa ″ (the arrangement pitch of the light spots SP) ≈Pa ′. The relationship of (1 unit arrangement pitch) / 4 is satisfied.

  This light receiving lens 222a also uses an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction. When a plurality of light spots SP are irradiated on the surface of the fixing belt 61 from the LED 211a in the main scanning direction, reflected light from the surface of the fixing belt 61 is generated. However, since the fixing belt 61 is not an optical mirror surface, reflection including a diffuse reflection component in addition to a regular reflection component occurs, and a part of the reflected light is guided to the light receiving lens 222a and then received by the PD 212a. The

  FIG. 8 is a plan view of the substrate 210a that supports the LEDs 211a and the PD 212a as observed from the z direction. The LEDs 211a are aligned with an arrangement pitch Pa in the main scanning direction within one unit, and are aligned with an arrangement pitch Pa 'in the main scanning direction between adjacent units. The PDs 212a are aligned with an arrangement pitch Pa '' 'in the main scanning direction. In addition, the interval between the LED 211a and the PD 212a in the sub-scanning direction is Pa ′ ″ ″. LED 211a-1, LED 211a-2,..., LED 211a- (N-1), LED 211a-N (in this embodiment, the number of units is 7) from the left end of the paper toward the positive x direction. Therefore, LED 211a-1 to LED 211a-28), and similarly, each PD 212a is moved from the left end of the paper in the positive direction of the x direction to PD 212a-1, PD 212a-2,..., PD 212a- (N '-1), PD212a-N' (similarly, PD212a-1 to PD212a-28).

<Comparative example>
[Configuration of reflective optical sensor]
Hereinafter, a specific example of the reflective optical sensor 200 ′ of the comparative example will be described with reference to FIGS. The configuration of the reflective optical sensor 200 ′ of the comparative example has the same configuration as that of the first embodiment except that the configuration described below is different. Detailed description of the same configuration as the first embodiment is omitted, and only a different configuration will be described.

(1) A light shielding wall 230 ′ is provided.
(2) The irradiation lens 221 ′ and the light receiving lens 222 ′ are arranged at the same position in the optical axis direction.
(3) The lens parameters (curvature radius, lens diameter, lens thickness, distance between the center of the irradiation system and the irradiation lens, distance between the centers of the light receiving system and the light receiving lens, etc.) are different.

  FIG. 10A is a schematic cross-sectional view of the reflective optical sensor 200 ′ observed in the main scanning direction (x direction). FIG. 10B is a schematic cross-sectional view of the reflective optical sensor 200 ′ of FIG. 10A observed in the sub-scanning direction (y direction). FIG. 11 is a schematic cross-sectional view of the PD 212 ′ and the light receiving lens 222 ′ of the reflective optical sensor 200 ′ observed in the sub-scanning direction (y direction). FIG. 12 is a diagram showing the lens array 220 ′ in more detail with respect to the reflective optical sensor 200 ′. FIG. 13 is a plan view showing the arrangement of the LEDs 211 ′ and PD 212 ′ on the substrate.

  As shown in FIGS. 10 to 13, the reflective optical sensor 200 ′ according to the comparative example irradiates the light spot SP on the surface of the fixing belt 61 with the light emitting diode (LED) 211 ′ as an irradiation system and the emitted light. The irradiating lens 221 ′ arranged so as to conduct light, the light receiving lens 222 ′ arranged so as to guide the reflected light reflected from the fixing belt 61, and the reflected light guided by the light receiving lens 222. A photodiode (PD) 212 ′ as a light receiving system for receiving light, a substrate 210 ′ that supports the LEDs 211 ′ and PD 212 ′, a lens array 220 ′ in which an irradiation lens 221 and a light receiving lens 222 ′ are integrated, and a substrate 210 'and lens case 220' are comprised, and the light shielding wall 230 for preventing flare light is comprised.

  A plurality of light shielding walls 230 ′ for preventing flare light are disposed between the LED 211 ′ and the irradiation lens 221 ′ in the main scanning direction. The light shielding wall 230 'and the case 240' are integrated by resin molding.

  FIG. 12 is a diagram showing in more detail only the lens array 220 ′ part of the reflective optical sensor 200 ′. The lens parameters of the irradiation lens 221 'will be specifically described. The radius of curvature of the irradiation lens 221' in the main scanning direction is 4.6 mm, and the conic constant in the main scanning direction is zero. The radius of curvature of the irradiation lens 221 in the sub-scanning direction is 4.3 mm, and the cone constant in the sub-scanning direction is −2.0. The irradiation lens 221 'has a lens diameter in the main scanning direction of 2.4 mm, a lens diameter in the sub scanning direction of 10.5 mm, and a lens thickness of 6.6 mm.

  The radius of curvature of the light receiving lens 222 'in the main scanning direction is 50 mm, and the conic constant in the main scanning direction is -1.0. The radius of curvature of the light receiving lens 222 'in the sub-scanning direction is 4.8 mm, and the conic constant in the sub-scanning direction is -1.6. The light receiving lens 222 'has a main scanning direction lens diameter of 17 mm, a sub scanning direction lens diameter of 10.1 mm, and a lens thickness of 6.6 mm.

  The distance between the centers of the irradiation lens 221 ′ and the light receiving lens 222 ′ in the sub-scanning direction (the distance between the optical axes) is 2.53 mm, and the distance between the centers of the irradiation system and the irradiation lens 221 ′ in the optical axis direction; The distance between the centers of the light receiving system and the light receiving lens 222 ′ in the optical axis direction is equal to each other and is 10.4 mm.

<Operation Example 1 of the Reflective Optical Sensor of the First Example>
Here, an example of the operation of the reflective optical sensor will be described according to the flowchart of FIG. 14 using the reflective optical sensor 200a of the first embodiment. A description will be given of processing performed for each member when it is desired to scan the light spot SP in the positive direction of the x direction in FIG. 8 on the fixing belt 61. The operation is the same for the comparative example and the following examples. In the first embodiment, the LEDs 211a-1 to 211a-28 are used to change the LEDs in each unit in the order of units 1 → 2 → 3 → 4 → 5 → 6 → 7 and from right to left on the page. So-called sequential lighting is performed in which lighting and extinguishing are repeated one by one.

  First, as shown in FIG. 14, L = 1 (1 ≦ L ≦ 7) is set as the initial value of the unit number (step S10). Next, h = 0 (0 ≦ h ≦ 3) is set as a counter for managing the lighting order of the LEDs 211a in the unit L (step S11). Then, in step S12, the LEDs 211a-n (n is a serial number of the LEDs 211a and is an integer of 1 ≦ n ≦ 28, and is expressed by n = 4L−h) are performed. For example, in the first processing, that is, when L = 1 and h = 0, since n = 4, the rightmost LED 211a-4 of the unit 1 is turned on. Next, the reflected light reflected by the fixing belt 61 is received by 2m (m is an integer satisfying 1 ≦ m ≦ 14) PDs 212a− (n−m) to PD212a− (n + m) (step S13). Details of the light reception will be described later. Thereafter, the LEDs 211a-n are turned off (step S14), and a detection signal is transmitted from each of the PDs 212a- (nm) to PD212a- (n + m) to the surface state determination means 300 (step S15).

  In step S16, it is determined whether h <3, that is, whether the processing in steps S12 to S15 has been executed for all four LEDs 211a in the unit L. If h <3 is yes, since there is an LED 211a that has not been processed, h is counted up (h = h + 1) (step S17), and then the process returns to step S12. And the process of step S12-S15 is repeated about next LED211a-n. On the other hand, if n <N is no, the process has been completed for all the LEDs 211a in the unit L, and the process proceeds to step S18. For example, in the unit 1, when the series of processes of turning on / off and transmitting the detection signal is completed for the LED 211 a-1 at the left end of the drawing in FIG. 8, it is determined that the process has been completed for all the LEDs 211 a in the unit 1.

  In step S18, it is determined whether L <7, that is, whether the processing in steps S11 to S17 has been executed for all units. If L <7 is yes, there is an unprocessed unit, so L is counted up (h = h + 1) (step S19), and the process returns to step S11. On the other hand, if L <7 is no, the process is completed for all units, and the process proceeds to step S20. In the present embodiment, when the processing for the left end LED 211a-25 of the seventh unit 7 is completed, one scan (one cycle) is completed. Finally, in step S20, it is determined whether the series of processes is repeated for another cycle. If yes, the process returns to step S10 and the processes of steps S11 to S19 are repeated. If no, the entire process is terminated.

  Next, the operation (step S13) of the PD 212a when the light spot SP is scanned in the positive x direction will be described. The reflected light from the fixing belt 61 is received by the plurality of PDs 212a in synchronization with the lighting of the n-th LED 211a-n (n is an integer of 1 ≦ n ≦ N = 28). Here, for simplicity, control is performed so that an even number of PDs 212a receive light. That is, 2m (m is an integer of 1 ≦ m ≦ 14) PDs 212a receive light.

Next, a method for selecting 2m PDs 212a will be described. When the n-th LED 211a-n is turned on, the PD 212a having the largest PD light reception amount and the PD 211a having the second largest PD light reception amount after the PD 212a are extracted from the N ′ (28) PDs 212a. In the arrangement of the PDs 212a as in the first embodiment, these two PDs 212a are adjacent to each other. If the center in the x direction of the two PDs 212a is set to X ₀ = 0, the remaining 2m−2 PDs 212a are The following formula X = 0 ± 1.5 l × P ′ ″ a
The PDs 212 arranged at the positions are extracted. Here, X represents a relative distance in the x direction from X ₀ , l represents an integer of 1, 2,..., M−1, and P ″ ′ a represents the first embodiment. This represents the arrangement pitch (see FIG. 8 and the like) of the PD 212a in the main scanning direction. Similarly, in the following second to fourth embodiments, the arrangement intervals of the PD 212a, PD 212b, PD 212c, and PD 212d in the main scanning direction are replaced with P ′ ″ b, P ′ ″ c, and P ′ ″ d. In the comparative example, it is replaced with P ′ ″. Further, 1.5 is a coefficient that is assumed even when the center-to-center distance between adjacent PDs 212a changes.

  The reflected light received by the 2m PDs 212a is photoelectrically converted by the PD 212a and amplified to a detection signal. The detection signal amplified by each PD 212a is sent to the surface state determination means 300 every time it is detected. In some cases, in order to increase the detection accuracy, it is possible to sequentially perform lighting over a plurality of cycles and perform an average value processing of detection results. Further, it is not necessary to use all N (28) LEDs 211a from the left end to the right end, and any N ′ ″ (1 ≦ N ′ ″ ≦ N = 28) out of N LEDs 211a to be turned on / off. May be used. When selecting N ′ ″, a series of adjacent LEDs 211 a may be used, but every other LED 211 a is selected depending on the position and size of the flaw, the size of the fixing belt 61 in the main scanning direction, and the like. Every two LEDs 211a may be used. Alternatively, one LED 211a in a non-scratched region and one or several LEDs 211a in a region where a scratch actually occurs may be used. Moreover, you may use LED211a of any one unit.

<Operation of surface condition determination means>
Next, operation | movement of the surface state determination means 300 is demonstrated using the flowchart of FIG. The surface state determination means 300 first receives detection signals from (2m + 1) PDs 212a of the reflective optical sensor 200a (step S20). Next, a detection result R-n corresponding to each LED 211a-n is calculated by taking the sum of the acquired detection signals. That is, the reflected light intensity can be acquired corresponding to each light spot SP irradiated in the main scanning direction, in other words, each position on the surface of the fixing belt in the main scanning direction (step S21).

  Next, the surface state of the fixing belt 61 is determined. In general, when the fixing belt 61 is scratched, the regular reflection component of the reflected light from the surface of the fixing belt 61 is decreased and the diffuse reflection component is increased as compared with the case where there is no scratch. In the reflective optical sensor 200a of the first embodiment shown in FIG. 5 and the like, and the reflective optical sensor 200 ′ of the comparative example shown in FIG. 10 and the like, the regular reflection component is reduced, so that the PD 212a and PD 212 ′ are changed. The amount of light received is reduced accordingly. Further, as the diffuse reflection component increases, a part of the amount of light received by the PD 212a and PD 212 'increases. As a result, when there is a scratch, the amount of light received by the PD 212a and PD 212 'is reduced compared to when there is no scratch. From the change in the amount of received light, the surface state, that is, the scratch level and the scratch position are calculated.

  First, the position of the scratch is determined. In the reflection type optical sensor 200a of the first embodiment, the reflected light intensity is obtained corresponding to each position on the surface of the fixing belt 61 in the main scanning direction. By comparing the intensity in the main scanning direction, it can be seen that there is a scratch at the position where the reflected light intensity is reduced. Here, a schematic diagram of the reflected light intensity obtained by the reflective optical sensor 200 ′ of the comparative example is shown in FIG. Specifically, the position of the flaw can be determined by taking a derivative of the reflected light intensity with respect to the main scanning direction (step S22) and obtaining a zero cross position where the derivative value greatly changes from negative to positive ( Step S23). FIG. 16B shows a schematic diagram in which the reflected light intensity is differentiated to obtain the zero cross position. In addition, when the absolute value of the differential value is smaller than a predetermined value set in advance, it indicates that the decrease in reflected light intensity is small, and it is determined that there is no flaw.

  As a specific example, N = 24, n = 3 to 22, m = 2, and LED 211 ′ arrangement pitch P = 1 mm with respect to the fixing belt 61 after passing 400,000 sheets in FIG. An example of a detection result Rn obtained using the reflective optical sensor 200 ′ of the comparative example is shown (step S21). In the reflective optical sensor 200 ′ of this comparative example, the light spot SP is irradiated onto the surface of the fixing belt 61 at a pitch of P ′ = 1 mm. Therefore, the horizontal axis in FIG. ]. FIG. 17B shows the result of differentiation with respect to the main scanning direction, specifically, the result of calculating the slopes at two points of R−n and R− (n + 1). Of course, for the purpose of smoothing, the slopes at three points of R- (n-1), R-n, and R- (n + 1) can also be calculated.

  When the zero-cross position is obtained based on FIG. 17B, n = 12.5, and there is a scratch at the position of 12.5 mm in the middle of the light spot irradiation position corresponding to the LED 211′-12 and the LED 211′-13. The determination can be made (the above corresponds to steps S22 to S24).

  Next, the scratch level (scratch depth) is determined (step S25). First, as the depth (roughness) of the scratch is deep (coarse), it is qualitatively considered that the decrease in the reflected light intensity is large, so the amount of decrease in the reflected light intensity may be obtained. FIG. 16C shows a schematic diagram showing the amount of decrease in reflected light intensity. In such a case as shown in FIG. 16C, the minimum value of the detection result R-n may be obtained simply, but depending on factors such as the attachment position of the reflective optical sensor 200 ′ and the inclination of the fixing belt 61. In some cases, an inclination component is superimposed on the detection result Rn. Therefore, the calculation is performed according to the following procedure.

First, a flawed position can be determined as n = 12.5 by the aforementioned steps S22 to S23 and FIG. On the other hand, a position without a flaw is a position where the fluctuation of the detection result R-n is small, that is, a position where the differential values are gathered around zero. That is, a position without a flaw can be calculated from the result of differentiation with respect to the main scanning direction. A detection result R-n ₀ at the position n ₀ with wounds, from the detection results _{R-n 1, R-n} 2 at position n _1, n ₂ without at least two wounds, the amount of reduction in reflected light intensity An example to be obtained is shown.

  For this purpose, in order to subtract the inclination component superimposed on the detection result R-n, the distance between the approximate straight line connecting the detection results at a plurality of positions without scratches and the detection result at the position with scratches may be obtained. . Actually, it is applied to the results of FIGS. 17A and 17B, and the amount of decrease in reflected light intensity is obtained. FIG. 18A shows a position where a plurality of points are collected in a range of ± 20 having a small differential value with respect to the position of the scratch based on FIG. 17B. From FIG. 18A, it is possible to select n = 6 and 15 as the positions having no scratch (step S26).

Therefore, the position n ₀ = 12.5 with a flaw and the positions n ₁ = 6 and n ₂ = 15 without a flaw are extracted, and the depth (roughness) of the flaw is obtained using each detection result R−n. ) Can be calculated (step S27). As shown in FIG. 18B, the broken line in the figure is a straight line connecting Rn-n ₁ and Rn-n _2, and the broken line arrow in the figure is the depth of the flaw. In this example, the depth of the scratch is 63.1. The reduction ratio of the reflected light intensity is 0.16 (16%). Moreover, it can be seen from FIG. 18B that the depth of the flaw is superimposed on the slope component indicated by the broken line. As the scratch level increases, this decrease in reflected light intensity increases.

  Next, a method for determining the width (size) of the scratch as another different parameter for determining the surface state will be described (step S28). First, the center position of the flaw can be determined by the above-described S22 to S23 and FIG. That is, from the detection result R-n at the position where there is a scratch, the reflected light intensity has a predetermined amount, for example, a 50% decrease, of the amount of decrease in the reflected light intensity corresponding to the depth (roughness) of the scratch. What is necessary is just to calculate a position. FIG. 19 is an enlarged graph of the vertical axis of FIG. From this result, it can be determined that the half width of the scratch is 3 mm (step S29).

  The surface condition parameters such as the flaw depth (steps S25 to S27) and the flaw width (steps S28 and S29) as described above may be determined, or only necessary parameters may be determined. Good. By determining all of the parameters, the state of the flaw can be determined in more detail. Moreover, the determination process can be quickly performed by determining only the necessary parameters.

<Comparison of effects between the first embodiment and the comparative example>
Experiments were performed using the reflective optical sensor 200 according to the first example of the present application shown in FIGS. 5 to 9 and the reflective optical sensor 200 ′ according to the comparative example shown in FIGS. FIG. 20 shows a graph of the fluctuation result of the PD output (light receiving unit output) at that time. This graph shows that when the fixing belt 61 is detected using two, four, six, eight and ten PDs 212a and 212 ', the lens arrays 220a and 220' are ± 50 μm in the sub-scanning direction. A PD output fluctuation result when only a deviation (a deviation angle is A) is applied to the fixing belt 61 alone is shown. As described above, the PD output is the sum of the detection values of the plurality of PDs 212a and 212 ′, and there is no change in the sub-scanning direction deviation Y and the tilt angle A of the lens arrays 220a and 220 ′ (Y = 0, A = 0) is normalized to 1. Hereinafter, this normalized value is referred to as a “median value”. Further, the PD output eliminates the influence of flare light, and there is almost no difference in light quantity between the reflective optical sensor 200 ′ of the comparative example and the reflective optical sensor 200a according to the first example of the present application.

  As apparent from FIG. 20, the reflection type optical sensor 200a according to the first example of the present application has a smaller PD output fluctuation due to the tilt angle fluctuation than the reflection type optical sensor 200 'of the comparative example. Further, even if the lens array 220a, which is considered to be generated when the lens array 220a is assembled to the light emitting / receiving device, has a deviation in the sub-scanning direction of about ± 50 μm, the tilt angle A may be a variation within ± 1.5 deg. For example, the fluctuation of the PD output is within ± 10% with respect to the median value.

  Further, as shown in FIG. 9, in the first embodiment, a flat portion (step) 223a is provided so that light is reflected by the flat portion 223a (two-dot chain line in FIG. 9). Arrow). This reflection reduces light other than the detection light (solid line arrow in FIG. 9) necessary for detection of the fixing belt 61 (shown by a dashed line arrow in FIG. 9, hereinafter referred to as “ghost light”). And the fall of the detection accuracy of the reflective optical sensor 200a can be suppressed.

  As described above, the reflective optical sensor 200a of the first embodiment of the present application has excellent optical performance. In the printer 100 according to the first embodiment using the reflective optical sensor 200a, the surface state determination unit 300 receives the detection signal from the reflective optical sensor 200a, so that the surface state of the fixing belt 61 is accurately determined. Can be detected. In the printer 100, based on the detection result of the surface state, for example, a large amount of toner is attached to a position corresponding to the scratch portion so as not to fix the recording paper in an area where the scratch is large. Thus, by implementing a control for making the scratches inconspicuous, it is possible to satisfactorily prevent deterioration in image quality. Further, when the level of scratches affects the image quality, the user can know when to replace the fixing belt 61 by issuing a warning such as a buzzer or a message display. Therefore, the fixing belt 61 is not replaced at a time when the image quality is not affected, and the fixing belt 61 can be used effectively.

<Second embodiment>
The configuration of the reflective optical sensor 200b according to the second embodiment will be described with reference to FIGS. FIG. 21A is a side view of the reflective optical sensor 200b of the second embodiment observed in the scanning direction (x direction). FIG. 21B shows the reflective optical sensor 200b in the sub-scanning direction ( It is the schematic sectional drawing observed in the y direction). FIG. 22 is a schematic sectional view of the PD 212b and the light receiving lens 222b of the reflective optical sensor 200b observed in the sub-scanning direction (y direction). FIG. 23 is a diagram showing the irradiation lens 221b and the light receiving lens 222b in more detail with respect to the reflective optical sensor 200b. FIG. 24 is a plan view of the substrate 210b that supports the LED 211b and the PD 212b as observed from the z direction.

  As shown in FIGS. 21 to 24, the reflective optical sensor 200 b of the second embodiment includes a light emitting diode (LED) 211 b as a light emitting unit (that is, an irradiation system), and radiated light on the surface of the fixing belt 61. A light receiving optical system having an irradiation lens 221b arranged to irradiate the light spot SP and a light receiving lens 222b arranged to guide the reflected light reflected from the fixing belt 61. A photodiode (PD) 212b as a light receiving unit that receives the reflected light guided by the light receiving lens 222b, a substrate 210b that supports the LEDs 211b and PD 212b, and a case 240b that holds the substrate 210b and the lens array 220b. Is composed of. Further, a flat portion (step) 223b is provided at the boundary between the irradiation lens 221b and the light receiving lens 222b.

  The configuration of the reflective optical sensor 200b of the second embodiment has the same configuration as that of the reflective optical sensor 200a of the first embodiment, except that the light receiving lens 222b is further away from the light receiving system. Yes. The printer of the second embodiment has the same configuration as that of the printer 100 of the first embodiment, except that the reflection type optical sensor 200b is used. Therefore, hereinafter, detailed description of the same configuration as that of the first embodiment is omitted, and only a different configuration will be described. The reflective optical sensor 200b of the second embodiment differs from the first embodiment in the following points by disposing the light receiving lens 222b further away from the PD 212b.

(1) Lens parameters (curvature radius, lens diameter, lens thickness, distance between the center of the irradiation system and the irradiation lens, distance between the centers of the light receiving system and the light receiving lens, etc.) are different.

  In the optical axis direction, the irradiation lens 221b and the light receiving lens 222b are approximately 0.5 mm apart from each other in the center of the lens, which is greatly deviated from the first embodiment. Compared with the light receiving lens 222b, the irradiation lens 221b is arranged at a position close to the irradiation system (LED 211b) side. Specifically describing the lens parameters, the radius of curvature of the irradiation lens 221b in the main scanning direction is 4.6 mm, and the conic constant in the main scanning direction is zero. The radius of curvature of the irradiation lens 221b in the sub-scanning direction is 4.3 mm, and the conic constant in the sub-scanning direction is −2.0. The irradiation lens 221b has a lens diameter in the main scanning direction of 2.4 mm, a lens diameter in the sub scanning direction of 9.2 mm, and a lens thickness of 6.6 mm.

  The radius of curvature of the light receiving lens 222b in the main scanning direction is 50 mm, and the conic constant in the main scanning direction is -1.0. The radius of curvature of the light receiving lens 222b in the sub-scanning direction is 4.8 mm, and the conic constant in the sub-scanning direction is −1.6. The light receiving lens 222b has a lens diameter in the main scanning direction of 17 mm, a lens diameter in the sub scanning direction of 10.9 mm, and a lens thickness of 5.6 mm.

  Further, the distance between the centers of the irradiation lens 221b and the light receiving lens 222b (inter-optical axis distance) in the sub-scanning direction is 2.53 mm, and the distance between the irradiation system (LED 211b) and the irradiation lens 221b in the optical axis direction is 10. The distance between the centers of the light receiving system (PD 212b) and the light receiving lens 222b in the optical axis direction is 11.37 mm.

  FIG. 25 shows a graph of PD output using the reflective optical sensor 200a of the first example and the reflective optical sensor 200b of the second example. This graph shows that when the fixing belt 61 is detected using two, four, six, eight, and ten PDs 212a and 212b, the lens arrays 220a and 220b are Y = ± 50 μm in the sub-scanning direction. The fluctuation result of the PD output when only the tilt angle A is applied to the fixing belt 61 alone is shown. The PD output eliminates the influence of flare light, and there is almost no difference in light quantity between the reflective optical sensor 200a of the first embodiment and the reflective optical sensor 200b of the second embodiment.

  Further, as apparent from FIG. 25, the reflection type optical sensor 200b of the second example has a PD output fluctuation caused by the fluctuation of the tilt angle change A, compared with the reflection type optical sensor 200a of the first example. It is getting smaller. Furthermore, even if a deviation in the sub-scanning direction of the lens array 220b, which is considered to occur when the lens array 220b is assembled to the light emitting / receiving device, occurs about Y = ± 50 μm, the tilt angle A is within ± 1.5 deg. If it is a fluctuation, the PD output fluctuation is within ± 10% of the median.

  As described above, the reflective optical sensor 200b according to the second embodiment has a variation in the tilt angle of the fixing belt 61 by disposing the light receiving lens 222b further away from the PD 212b as compared with the first embodiment. The resulting PD output fluctuation can be reduced more satisfactorily.

<Third embodiment>
The configuration of the reflective optical sensor 200c according to the third embodiment will be described with reference to FIGS. FIG. 26A is a schematic cross-sectional view of the reflective optical sensor 200c of the third embodiment observed in the sub-scanning direction (y direction), and FIG. 26B shows the reflective optical sensor 200c in the sub-scanning direction. It is the front view observed in the direction (y direction). FIG. 27 is a schematic cross-sectional view of the PD 212c and the light receiving lens 222c of the reflective optical sensor 200c observed in the sub-scanning direction (y direction). FIG. 28 is a plan view of the substrate 210c that supports the LEDs 211c and the PD 212c as observed from the z direction.

  As shown in FIGS. 26 to 28, the reflective optical sensor 200 c according to the third embodiment includes a light emitting diode (LED) 211 c as a light emitting unit (that is, an irradiation system) and radiated light on the surface of the fixing belt 61. An irradiation optical system having an irradiation lens 221c arranged to irradiate the light spot SP, and a light receiving lens 222c as a light receiving unit arranged to guide the reflected light reflected from the fixing belt 61. A light receiving optical system, a photodiode (PD) 212c that receives reflected light guided by the light receiving lens, a substrate 210c that supports the LEDs 211c and PD 212c, and a case 240c that holds the substrate 210c and the lens array 220c. Composed. Further, a flat portion (step) 223c is provided at the boundary between the irradiation lens 221c and the light receiving lens 222c.

  The configuration of the reflective optical sensor 200c of the third embodiment is the same as that of the first embodiment except that the light receiving lens 222c is a cylindrical lens having no power in the main scanning direction instead of the anamorphic lens. It has the same configuration as the sensor 200a. The printer of the third embodiment has the same configuration as that of the printer 100 of the first embodiment, except that this reflection type optical sensor 200c is used. Therefore, hereinafter, detailed description of the same configuration as that of the first embodiment is omitted, and only a different configuration will be described.

  Specifically, the lens parameters in the third embodiment are the same as those in the first embodiment and the second embodiment for the irradiating lens 221c, and there is no change. On the other hand, since the light receiving lens 222c of the third embodiment uses a cylindrical lens that focuses light only in one axial direction, only the radius of curvature in the main scanning direction and the conical constant in the main scanning direction are the first, This is different from the second embodiment, and the radius of curvature of the light receiving lens 222c in the main scanning direction is ∞, and the conic constant in the main scanning direction is 0.

  As shown in FIGS. 6 and 12, the reflective optical sensor 200a of the first embodiment and the reflective optical sensor 200c of the third embodiment have a configuration in which a plurality of PDs 212a and 212c are arranged in the main scanning direction. . Therefore, with respect to the sub-scanning direction, it is necessary to focus light incident on the PD in the sub-scanning direction in consideration of the PD position and the PD size. However, since a plurality of PDs are arranged in the main scanning direction, it is deliberate. It is not necessary to focus light by providing power in the main scanning direction of the light receiving lens.

  Therefore, in the third embodiment, as described above, the light receiving lens 222c is a cylindrical lens having no power in the main scanning direction. With this configuration, it is possible to further suppress a change in the PD light reception amount distribution due to a difference in the LED 211c that is lit compared to the case where an anamorphic lens is used. Therefore, the surface state of the fixing belt 61 can be detected with higher accuracy.

<Fourth embodiment>
The configuration of the reflective optical sensor 200d according to the fourth example will be described with reference to FIGS. FIG. 29A is a schematic cross-sectional view of the reflective optical sensor 200d of the fourth embodiment observed in the main scanning direction (x direction). FIG. 29B is a schematic cross-sectional view of the reflective optical sensor 200d observed in the sub-scanning direction (y direction). FIG. 30 is a schematic sectional view of the PD 212d and the light receiving lens 222d of the reflective optical sensor 200d observed in the sub-scanning direction (y direction). FIG. 31 is a diagram showing the irradiation lens 221d and the light receiving lens 222d in more detail with respect to the reflective optical sensor 200d. FIG. 32 is a diagram of the substrate 210d that supports the LED 211d and the PD 212d as observed from the z direction.

  As shown in FIGS. 29 to 32, the reflective optical sensor 200d according to the fourth embodiment includes a light emitting diode (LED) 211d as a light emitting unit (that is, an irradiation system) and the emitted light on the surface of the fixing belt 61. The light is guided by the irradiation lens 221d arranged to irradiate the light spot SP, the light receiving lens 222d arranged to guide the reflected light reflected from the fixing belt 61, and the light receiving lens 222d. A photodiode (PD) 212d as a light receiving unit that receives the reflected light, a substrate 210d that supports the LEDs 211d and PD 212d, a lens array 220d in which the irradiation lens 221d and the light receiving lens 222d are integrated, a substrate 210d, and A case 240d for holding the lens array 220d and an opening O for preventing flare light (see FIG. 1 reference) and a light shielding wall 230d for forming, and a. Further, a flat portion (step) 223d is provided at the boundary between the irradiation lens 221d and the light receiving lens 222d.

  The configuration of the reflective optical sensor 200d of the fourth embodiment is the same as that of the reflective optical sensor 200c of the third embodiment, except that an opening O (light shielding wall 230d) for preventing flare light is provided. have. The printer of the fourth embodiment has the same configuration as the printer 100 of the first embodiment except that this reflective optical sensor 200d is used. Therefore, hereinafter, detailed description of the same configuration as that of the first embodiment is omitted, and only a different configuration will be described.

  In the reflective optical sensor 200d of the fourth embodiment, a light shielding wall 230d is provided around the irradiation lens 221d to form an opening O, whereby an irradiation lens other than the irradiation lens 221d corresponding to the arbitrary LED 211d to be lit is used. Light that passes through the lens 221d and irradiates the fixing belt 61, or the lens surface of the irradiation lens 221d other than the irradiation lens 221d corresponding to the arbitrary LED 211d to be lit or the irradiation lens 221d corresponding to the arbitrary LED 211d to be lit. It is possible to prevent flare light such as direct reflected light from directly entering the PD 222d. Therefore, the surface state of the fixing belt 61 can be detected with higher accuracy.

  The opening O (light shielding wall 230d) and the case 240d can be integrated by resin molding.

  Further, when the opening O (the light shielding wall 230d) is provided, the flat portion (step) 223d is used as the reference plane. Thereby, the positional accuracy of the opening O (light shielding wall 230d) is improved, and the performance deterioration of the reflective optical sensor 200d can be suppressed. Further, by arranging the opening O (light shielding wall 230d) in the vicinity of the flat portion (step) 223d with respect to the sub-scanning direction, it is possible to eliminate light that is transmitted through the light receiving lens 222d and incident on the fixing belt 61. . In addition, the light that passes through the irradiation lens 221d, further passes through the light receiving lens 222d, and is incident on the fixing belt 61 is reflected by the flat portion (step) 223d and separated from the detection light in the sub-scanning direction. It is possible to guide the light. Therefore, in the reflective optical sensor 200d of the fourth embodiment, excellent detection accuracy can be maintained.

  The reflective optical sensors 200b, 200c, and 200d of the second to fourth embodiments can be sequentially turned on by the operation described in the operation example 1 of the reflective optical sensor 200a of the first embodiment. The operation of the reflective optical sensor according to the present application is not limited to this. Hereinafter, another different operation example 2 of the first to fourth embodiments will be described.

<Example 2 of operation of reflective optical sensor>
An operation example 2 of the reflective optical sensor 200 (200a, 200b, 200c, 200d) of the first to fourth embodiments will be described. In this operation example 2, the light scanning line period in the main scanning direction can be shortened by simultaneously lighting a plurality of LEDs. FIG. 33 shows a PD output result when this operation example 2 is performed.

  For example, if the number of units consisting of four LEDs and one irradiation lens is nine, unit 1, unit 2,..., Unit from the left end in the positive direction of the x axis (right direction on the page). Assume that 9 is arranged. Further, three PDs are additionally arranged at the left end of the unit 1 and the right end of the unit 9, respectively. When the surface state of the fixing belt 61 is detected using the reflective optical sensor 200 configured in this way, the LEDs of the units 2 to 8 are turned on. Within each unit, four LEDs are arranged in the positive x-axis direction. It is assumed that LED1, LED2, LED3, and LED4 are arranged in this order with relative numbers in the unit. Hereinafter, for example, the LED 3 in the unit 2 is referred to as an LED 2-3. In addition, it is assumed that the PD is 9 units and the additional 6 and a total of 42 PDs are arranged in the order of PD_1, PD_2,..., PD_42.

  FIG. 33A shows a PD output distribution in a plurality of PDs when the LED 2-3 is turned on. The PD output is normalized to 1 at the maximum value, and the PD outputs in PD_1 to PD_4 and PD_15 to PD_18 are 0. Therefore, when the LED 2-3 (LED 2-2) is turned on, the number of PDs (PD_5 to PD_14) may be ten.

  For example, when two LEDs are turned on at the same time, when any one LED is turned on, the remaining one LED that is not any one LED is lit on the ten PDs used as the sensor detection results It is necessary that no reflected light is received. Therefore, when lighting a plurality of LEDs at the same time, it is preferable to use LEDs that are arranged at some distance in the main scanning direction.

  FIG. 33B shows PD output distributions in a plurality of PDs when the LED 2-3, the LED 5-3, and the LED 8-3 (the third LEDs of the units 2, 5, and 8) are simultaneously turned on. Even if these three LEDs are turned on at the same time, the output received by any one PD is received by any one of the multiple PDs that receive the reflected light when the single LED is turned on. Is equal to the output.

  In the example shown in FIG. 33 (b), the LEDs 1 of the units 2, 5, and 8, the LEDs 2 of the units 2, 5, and 8, the LEDs 3 of the units 2, 5, and 8, and the LEDs 4 of the units 2, 5, and 8 are turned on simultaneously. Is possible. The LEDs 1 of the units 3 and 6, the LEDs 2 of the units 3 and 6, the LEDs 3 of the units 3 and 6, and the LEDs 4 of the units 3 and 6 can be turned on simultaneously. The LEDs 1 of the units 4 and 7, the LED 2 of the units 4 and 7, the LED 3 of the units 4 and 7, and the LED 4 of the units 4 and 7 can be turned on simultaneously.

  Thus, by simultaneously lighting a plurality of LEDs, the line period of optical scanning in the main scanning direction can be shortened. If the line cycle can be shortened, the conveyance speed of the fixing belt can be increased, and the time required for the image forming operation can be further shortened.

<Arrangement angle of reflective optical sensor>
In the first to fourth embodiments, the reflective optical sensor 200 (200a, 200b, 200c, 200d) is disposed in parallel to the main scanning direction of the fixing belt 61. However, the present application is not limited to this, and the reflective optical sensor 200 may be arranged in a direction crossing the main scanning direction as another different arrangement form. With such an arrangement, the arrangement pitch of the light spots SP in the main scanning direction can be reduced. FIG. 34A shows the irradiation position SP of the light spot SP when the reflective optical sensor is arranged in parallel to the main scanning direction, and FIG. 34B shows the arrangement in a direction intersecting the main scanning direction. The irradiation position of the light spot SP is shown.

  In FIG. 34 (b), the reflection type optical sensor is arranged so as to intersect so that the angle formed by the longitudinal axis and the main scanning direction is 45 °. Thereby, although the detection area A 'in the main scanning direction is shortened to 1 / √2, the arrangement pitch of the light spots SP in the main scanning direction can also be decreased to 1 / √2. Therefore, the position resolution of the detection result of the reflective optical sensor can be further improved by detecting a narrower detection area A ′ with the same number of light spots SP than in the case of FIG. it can. This angle is not limited to 45 °, and can be set to an appropriate angle according to the width of the scratch. In the present embodiment, the reflective optical sensor 200 itself is inclined with respect to the main scanning direction, but the present invention is not limited to this. As another different embodiment, the reflective optical sensor 200 is arranged in parallel to the main scanning direction so that the light spot row is inclined as shown in FIG. It may be irradiated. Even in this case, the same effect can be obtained.

  As described above, in the first to fourth embodiments, it is impossible in the prior art by disposing the reflection type optical sensors 200a, 200b, 200c, and 200d as described above in the image forming apparatus (printer 100). Further, it is possible to detect a flaw on the fixing belt in real time and to detect a flaw position and a flaw width on the fixing belt. Further, by optimizing the light receiving section and light emitting section for the reflective optical sensors 200a, 200b, 200c, and 200d and the optical system for the sensor, adjacent light spots on the fixing belt 61 that is the test object. While maintaining the SP interval, the intensity of reflected light from the fixing belt 61 can be increased to improve the detection accuracy of the surface of the fixing belt 61.

  A preferred arrangement of the reflective optical sensors 200a, 200b, 200c, and 200d of the first to fourth embodiments with respect to the fixing belt 61 will be described. These reflective optical sensors 200a, 200b, 200c, and 200d are regions Edg through which the edge portion in the paper width direction of small-size paper among the paper used in the printer 100 passes, as shown in each drawing of FIG. It is preferable to arrange in the vicinity. In FIG. 35A, the detection area A includes the passage area Edg at the edge in the paper width direction even if the length of the detection area A in the main scanning direction is shortened. be able to. Since the detection area A can be shortened as described above, there is an advantage that the reflective optical sensor 200 can be downsized particularly in the main scanning direction. The width of the scratch is about several hundred μm to several mm, and the variation range as the position of the scratch is about several mm. For this reason, the detection area A is preferably about 5 mm to 15 mm in the main scanning direction.

  In the image forming apparatus of the present application, for example, a plurality of sizes of paper such as A3 size, A4 size, and A5 size can be used. In general, there are a large number of sheets that can be passed through the maximum length in the A3 vertical direction. Therefore, the small size sheet width here refers to the sheet size excluding the A3 sheet. If the image forming apparatus is capable of A2 portrait paper, paper sizes other than A2 paper are targeted.

  Further, since there are two passage areas Edg at the edges in the paper width direction of the small size, as shown in each drawing of FIG. 35, one is provided at each edge of the paper, that is, in the main scanning direction. Two reflective optical sensors 200-1 and 200-2 may be arranged. Such an arrangement makes it possible to more reliably detect scratches. However, the present application is not limited to this, and the vertical streak caused by the end face of the paper occurs on both sides of the paper, and generally there is no significant difference in the scratch level. You may arrange | position only in any one (one side), and the cost reduction of an installation is attained.

  In the image forming apparatus of the present application, the reflection type optical sensor 200 (200a, 200b, 200c, 200d) described in each embodiment is formed large in the main scanning direction as shown in FIG. The size may be almost the same as the width of 61, and can correspond to various paper sizes. For example, in the case of an image forming apparatus capable of A1 longitudinal paper, edge portions in the width direction of A2 size, A3 size, A4 size, A5 size, B3 size, B4 size, B5 size, and B6 size paper The reflective optical sensor is formed large in the main scanning direction so that the passage region Edg can be irradiated by the reflective optical sensor 200. By forming in this manner, it is possible to cope with various paper sizes and to detect the surface state with high accuracy. Note that when operating such a reflective optical sensor 200, all the LEDs may be used, or only a part may be lit according to the size of the detection area. Further, for example, an area through which the edge portion of the paper passes based on the size information of the paper that is currently passed through, which is detected by the printer main body or the like so as to cope with a change in the size of the paper that is passed through. Only nearby LEDs may be used. With such a configuration, the energy efficiency of the LED can be improved, and the state of scratches by the edge portion can be detected with high accuracy.

  As the fixing member (moving body), any conventionally known fixing member may be used, but it is preferable to use it for detecting the surface state of the endless belt-like fixing belt 61 as in the above embodiments. is there. Since the surface of the fixing belt is made of a material having a high surface hardness such as PFA, the surface is particularly easily damaged. Also, the reflection angle of the reflected light may vary depending on the detection position due to the surface state being non-uniform in the sub-scanning direction, the internal stress being non-uniform in the sub-scanning direction, or the presence of joints. . However, according to the image forming apparatus provided with the reflective optical sensor of the present application, it is possible to accurately detect the surface state even with the fixing belt whose detection accuracy changes in the sub-scanning direction.

  The image forming apparatus including the reflective optical sensors of the first to fourth embodiments has been described above. However, these embodiments are merely examples, and the present application is not limited thereto. A reflective optical sensor that can irradiate the surface of the fixing unit with a plurality of light spots in the main scanning direction and receive the reflected light can accurately detect the surface state of the fixing belt, The problem of the present application can be solved.

  The reflective optical sensor described in each embodiment is an array type in which a plurality of LEDs and a plurality of PDs face each other in a one-to-one relationship. However, the laser is deflected by an optical deflector and is applied from the surface of the fixing belt. A light deflection type in which reflected light is received by one or a plurality of PDs may be used. Further, a sensor driving type in which a reflective optical sensor composed of one LED and one PD is moved in the main scanning direction by an appropriate driving unit may be used.

61 Fixing belt (moving body)
100 printer (image forming apparatus)
200, 200a, 200b, 200c, 200d, 200-1, 200-2 Reflective optical sensors 211a, 211b, 211c, 211d LED (light emitting unit, irradiation system)
221a, 221b, 221c, 221d Irradiation lens 222a, 222b, 222c, 222d Light reception lens 212a, 212b, 212c, 212d PD (light receiving part)
210a, 210b, 210c, 210d Substrate 220a, 220b, 220c, 220d Lens array 223a, 223b, 223c, 223d Flat portion 230d Light-shielding wall (for opening formation)
300 Surface condition determination means S Recording paper (recording medium)
SP light spot O opening

Japanese Patent Laid-Open No. 5-113737 JP 2007-34068 A JP 2006-251165 A

Claims (10)

A reflective optical sensor that is used in an image forming apparatus that forms an image on a recording medium and detects a surface state of a moving body,
A plurality of irradiation systems having at least two light emitting units;
An irradiation optical system having a plurality of irradiation lenses corresponding to the plurality of irradiation systems, and guiding the light emitted from the irradiation system to the moving body;
A light receiving system having at least two light receiving portions;
A light receiving lens corresponding to at least two of the light receiving parts, and a light receiving optical system for guiding the light reflected by the moving body to the light receiving system,
The plurality of irradiation lenses and the light receiving lens are integrated with each other and arranged such that the center of the lens is different with respect to the optical axis direction, and between the irradiation lens and the light receiving lens. A reflective optical sensor having a flat portion parallel to the optical axis direction at a boundary portion.   2. The reflective optical sensor according to claim 1, wherein the light emitting units of the irradiation system are arranged line-symmetrically with respect to an optical axis of the corresponding illumination lens.   3. The reflective optical sensor according to claim 1, wherein the light receiving lens is disposed at a position away from the light receiving system with respect to an optical axis direction as compared with the irradiation lens.   The reflective optical sensor according to claim 1, wherein the light receiving lens is a cylindrical lens that focuses light in only one axial direction.   The reflective optical sensor according to any one of claims 1 to 4, wherein an opening is provided between the irradiation system and the illumination optical system.   The reflective optical sensor according to any one of claims 1 to 5, wherein a light spot is sequentially irradiated onto the surface of the movable body from the light emitting units of a plurality of the irradiation systems.   The reflective optical sensor according to any one of claims 1 to 5, wherein a light spot is simultaneously irradiated onto the surface of the moving body from the light emitting units of a plurality of the irradiation systems.   Reflection as described in any one of Claims 1-7 which irradiates a several light spot with arbitrary inclination with respect to the detection direction of the surface of the said mobile body from the said light emission part of the said several irradiation system. Type optical sensor.   An image formation using the reflection type optical sensor according to any one of claims 1 to 7 as a reflection type optical sensor for detecting a surface state of a moving body for fixing an image on a recording medium. apparatus.   The image forming apparatus according to claim 9, wherein the moving body is an endless belt-shaped fixing belt.